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Exam 1 key - NAME EXA M 1 75 points CHEM 214 Fall 2007 1(20...

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Unformatted text preview: NAME: _ EXA... M # 1_ 75 points CHEM 214, Fall 2007 1. (20 pts) Answer the following questions. 2 ~-s 1. A 35.0 nanograms per liter of Cadmiun solution is equal t0 0--=,-,.'-'..J~ ~,-,-~O'- \ paris per million (ppm) . 2. 95% confidence limits are {larger, the same as ,Eal~ than 99% confidence limits for the same experiment. 3. Suppose that 0.50 mg of precipitate is lost as a result of washing with liquid. What type of error is associated with the weight of precipitate after drying the sample in a gravimetric analysis? SJSCem at lL· 4. For an ideal Gaussian distribution, about gj .) % of the measurements lie within two standard deviations on either side of the mean (i.e. in the interval fl ± 20). 5. In volumetric glassware, 'I'D means to doAl&J t!J( and 1fC means -b D sr rJ-rJ. i f\ 6. A reference material is known to contain 89.5% Zinc. Two groups of students performed the analysis on the reference material and obtained the following data: Group 1 Group 2 89.5 80.1 100.5 79.3 88.2 81.2 84.2 80.9 99.9 79.6 78.5 81.1 Average 90.1 80.4 standard deviation 8.7 0.8 What can you tell about the accuracy and precision of the data from group I ? From group 2? Use the following descriptions; (a) Precise but not accurate (b) Accurate but not precise (c) Both accurate and precise (d) Can not tell if accurate or precise based only on the given information Answer: Group 1 --"=--'f-L--b'-------------- Group 2 Ii)...
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Exam 1 key - NAME EXA M 1 75 points CHEM 214 Fall 2007 1(20...

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